Process for the production of textile materials



Patented Nov. 28, 1950 PROCESS FOR THE PRODUCTION OF TEXTILE MATERIALS Thomas Jackson, Spondon, near Derby, England, assignor, by mesne assignments, to Celanese Corporation of America, a corporation of Delaware No Drawing. Application April 5, 1945, Serial No. 586,815. In Great Britain April 20, 1944 11 Claims. (01. 18-54) This invention relates to the production of artificial filaments and particularly to the production of artificial cellulosic filaments which are especially valuable for use in the manufacture of tires and other articles coated with natural or synthetic rubber. It also relates to the coating of such filaments with rubber.

In the production of articles comprising yarns coated with rubber it is of great importance that the rubber should adhere firmly to the filaments or fibres of which the yarns consist. This can be eiiected without great difficulty when cotton yarns are employed but'it is much more diificult when yarns made of artificial cellulosic filaments are used, particularly if the filaments are regenerated cellulose filaments of high tenacity such as may be obtained by the saponification of stretched yarns made of cellulose acetate. This is especially unfortunate as the high tenacity of such yarns and their good resistance to heat renders them in other respects particularly suitable for use in the production of tires and other rubber-coated articles which are subjected to rapid and severe fluctuations of stress.

'With a view to overcoming the above difliculty various methods have been described for increasing the adhesion between artificial cellulosic filaments and rubber. For instance, it has been proposed to treat the filaments with'compositions containing thermosetting synthetic resins or proteinaceous substances, usually in conjunction with rubber latex. This method. however, not only involves an additional operation but also is liable to cause the individual filaments to adhere to one another and to reduce the resistance of the finished article to fatigue.

I have now discovered a novel method for theproduction of rubber-coated articles by which improved adhesion between artificial cellulosic filaments and rubber may be obtained without the necessity for the additional operation involved when resins or the like are. employed and without the risk referred to above of causing adhesion of the filaments and reducing fatigue resistance.

According to the present invention rubbercoated articles are produced from a special type of artificial celluldsic filaments which differ from the filaments commonly employed for textile purposes in that they have a roughened surface. Such filaments, which may be used, forinstance, in the form of cords or fabrics, yield rubbercoated articles in which the adhesion between the rubber and the filaments is very satisfactory.

The filaments may be produced by various z methods, e. g. by surface abrasion as described in U. S. Patent No. 1,957,508, but it is preferred to employ roughened filaments produced by the novel process described in the present specifica tion, according to which stretched filaments of high tenacity made of organic derivatives of cellulose or regenerated cellulose and containing a finely divided substance are subjected to treatment to remove some at least of the particles of the substance, thus producing filaments which are pitted superficially.

Such pitted filaments, in which the roughening is due to the removal of small particles embedded in the surface, are characterised by numerous depressions of a more or less circular form. This type of rougheningwhich is quite characteristic and is easily distinguishable under the microscope from that produced by abrasion, has been found to be particularly effective in improving adhesion.

The filaments which are of the greatest value for the production of the coated articles are regenerated cellulose filaments obtained by the saponification of stretched filaments made of organic acid esters of cellulose. Such filaments are preferably produced by removing the finely divided substances after saponification, though removal may be efiected prior to or durin saponification.

'The invention includes the coating with rub-- ber of cords, fabrics and other articles comprising roughened filaments. It also includes the novel-methods described herein for the production of roughened or pitted" filaments which have a high tenacity and which are of particular value in the production of rubber tires and other rubber-coated articles.

- The invention is concerned with the produc-' tion of articles which are impregnated with rubber. as well as those which are only superficially coated and the terms ,rubber-coated and the like'are to be understood as covering both types of processes.

. The production of filaments containing a finely witha-dispersicn of a suitable substance where-' by-it-;is: absorbed by the filaments. When the finely-divided substance is present in the spinning solution from which the materials'are produced, spinning maybecarriednut by eitheria dry-spinning or a wet-spinning method. If a wet-spinning method is employed it is necessary to choose a finely divided substance which will not be dissolved, at least to any substantial extent, by.the coagulating bath employed.

When a finely divided substance is incorporated in the spinning solution its particle size must be sufficiently small to avoid any risk of clogging of the jet orifices. Thus with filaments of normal denier spun from orifices having diameters of 0.05 to 0.08 mm. the particles should have a diameter not greater than .003 mm., preferably about .001 to .002 mm. If, however, the

finely divided substances are incorporated in the filaments after their formation the sizes of the 4 substance is removed from the filaments before the stretching operation the pitting of the stretched filaments is not satisfactory. In order therefore that satisfactory products may be obtained without the use of excessive proportions of the substance it is desirable that the substance which is employed should be substantially insoluble in any liquids with which the filaments are liable to come into contact prior to and during the stretching operation. Further, it is important that the substance should be easily solparticles may be considerably higher, for examuble in a liquid which can be applied to the artificial filaments for the removal of the substance without damaging the filaments themselves. For most purposes inorganic substances are best both from the point of view of cheapness and also for ease of removal. I hey should not, as a rule, be

quent to their formation in order to introduce the finely divided substance, it is desirable that the treatment should be effected'while they are in a swollen condition. Thus hanks of cellulose acetate yarn may be swollen in an aqueous solution of acetone, dioxane or acetic'acid-and then immersed in a suspension of a suitable substance or they may be immersed directly in such a suspension in a liquid having a swelling action on the cellulose acetate. According to another method a finely divided substance may be formed in situ by the interaction of two reagents. Thus filaments spun from a solution containing one of the reagents may be treated with the other reagent to form the finely divided substance; For. example, cellulose acetate fi aments containin calcium chloride may be treated with a solution of sodium carbonate so as to form calcium carbonate in the filaments.

Whichever method is employed for the production of the fi aments containing the finely divided substance, it is not'necessary that the pro- .1

portion of-the substance should be very high. Usually proportions of less than 5%, for example 3%, 1% 'or even less are sufiicient, particularly if the substances are concentrated mainly in the surface of the filaments, as may be the case if they 'are incorporated or formed in the filaments by an after-treatment process. It will be appreciated that provided that the surface layers of the filaments contain sufficient of the'finely divided substance to "give a satisfactory pitting of the filaments when it is removed, it is not of great importance whether the substance is also present in the core of the filaments. Indeed, the use of filaments containing finely divided substances only in their surface layers is advantageous in somerespects. For example, the proportion of substance to filament bas'e required to give the same degree of surface roughening is smaller than whenthe substance is distributed throughout the filaments and a possible loss in tenacity due'to the presence of the substance in the interior of the roughened filaments is avoided. Further, filaments containing the substances only in the surface layers are produced by aftertreatment methods as described above, which renders it possible to use substances of larger particle size than when the substances are present in the spinning-solutions.

than those of roughened filaments obtained from.

filaments containing finely divided substances I In consequence such filaments may have larger surface pores easily water-soluble otherwise they may be removed during the stretching operation, but it is desirable that they should be soluble in dilute solutions of acids or alkalies. They may then be removed by a treatment of the stretched filaments either in an operation applied specifically for this purpose or during saponification, if the finely divided materials are soluble in the saponifying medium, e. g.'in aqueous or alcoholic sodium hydroxide or ethylene diamine or other organic base. In many'cases carbonates, oxides or hydroxides are very suitable substances, for example'barium carbonate, barium oxide, beryllium carbonate, beryllium hydroxide, bismuth hydroxide, calcium carbonate, calcium hydroxide, lead carbonate, lead hydroxide, magnesium carbonatefzinc carbonate, and zincv hydroxide. Other'substances which may be employed are boric acid, 'basic aluminium acetate, barium ortho-phosphate, barium s'ulphite, and calcium aluniinate.

As has: already been stated the invention is particularly concerned with the production of filaments of high tenacity having a basis of regenerated cellulose. Suchfilaments are best obtained by stretching and saponifying ordinary dry-spunfilame'nts made of acetone-soluble cellulose acetate or other lower fatty acid ester,

a an organic softening agent, for instance acetone or dioxane, but the preferred method 'of stretching is to carryit out during their passagethrough a vessel containing hot water orfwet steam at a temperature above C., particularly 1 30 to c. Erocesses of this character ar QQSQribed in U. 5. Patents Nos. 2,1 l2,72 l, 2,1 l 2ij72 2. and 2,142,909.. For high degrees of stretch the method of stretching described. in the last speci; fication, in which the filaments pass firstv through an end chamber containing an, inert fiuid under press and he hro h, a'stlt tchmg hem: befcqntairfing t. steam or hot Wa er-u d r. P essu e i of a t e a edance 1 1 9 an operation the end chamber may contain air or other inert gas-under pressure but preferably water is employed. Eilaments having a basis of an 1 Or an dsr e r of 5 9 .4a? l s 9 tained" by 'these processes which; have tenacities OfS-or 4' grams per denier or eten Qahdthe tenacities may b'still 'further iner-eased; e. g.

to 4 or 5 grams per denier or more, by completely saponifying the filaments, for example with a solution of sodium hydroxide, ethylene diamine or other inorganic or organic base. For example, filaments having tenacities of 5 or 6 grams per denier may be obtained by stretching cellulose acetate filaments to ten times their original length in wet steam at 130 to 135 C. and then completely saponifying them in a solution of so dium hydroxide containing sodium acetate. Even higher tenacities, e. g. 5 to 6 grams per denier in the case of cellulose acetate filaments and 8 to 9 grams per denier in the case of regenerated cellulose filaments, may be obtained from cellulose derivatives of high viscosity, as described in British specification No. 557,004.

As indicated above the finely divided substances employed are preferably soluble in dilute solutions of acids or alkalies. Removal of the sub stances may be effected at any stage after stretching but when the filaments are to be saponified it is preferably effected after saponification. The removal may be carried out during the passage of the filaments through a suitable liquid or by immersing them in hank form in such a liquid,

e. g. in a dilu e aqueous solution of hydrochloric acid, in aqueous acetic acid or in an aqueous solution of sodium hydroxide.

Hitherto the regenerated cellulose filaments referred to have been those obtained from filaments made of organic esters of cellulose. Such filaments are preferred, since by the method employed for their production filaments of higher tenacity are obtainable than when other methods, using for instance viscose or cuprammonium solutions, are adopted. Moreover, the production of roughened filaments by the removal of finely divided substances presents greater difiiculties when the viscose or cuprammonium process is employed, as suitable inorganic substances are usually either soluble in the alkaline spinning solution or the acid coagulating bath or are converted into insoluble compounds by such acid bath. Solid organic compounds, e. g. anthracene, may be employed and may be removed from the filaments with suitable organic solvents but such methods are usually more complicated and exensive than those applicable when the filaments are produced from organic esters or cellulose.

The filaments used in the production of the yarns, cords or other articles to which the rubber-coating is to be applied may be in the form of long continuous filaments or in the form of staple fibres. Conversion of continuous filaments into staple fibres may be effected at any suitable stage after the stretching operation, preferably after saponification, if this is effected.

Though the greatest value of the pitted filaments produced by the process of the present invention lies in their use in the production of rubber-coated articles, they can also be employed for other purposes, e. g. for the production of effect fabrics.

The association of roughened filaments in accordance with the present invention for the production of cords, fabrics or other articles and the coating of these articles with rubber may be carried out in the usual manner. The articles may consist wholly of roughened filaments having a basis of a cellulose derivative or of regenerated cellulose, or these filaments may be associated with other filaments, for example with filaments made of natural cellulose materials such as cotton. In order to improve still further the adhesion between the filaments and rubber, the

6 filaments may be treated by the process described in U. S, Patent application S. No. 534,810, now abandoned, according to which regenerated cellulose fibres are treated with a solution of rubber in a hydrophobe liquid and the moisture content of the material is reduced immediately before or durin the treatment.

The invention is of value for the production of rubber-coated articles of many kinds, e. g. tires, macintoshes and other wateror gas-proofed f abrics, woven or knitted rubberised fabrics for the production of wearing apparel and circular woven or braided fabrics for fire hoses. Any rubber may be employed in the production of rubber-coated articles according to the present invention, the term rubber being employed to cover natural rubber and other rubber-like substances such as gutta-percha and balata; filmforming derivatives of rubber such as rubber hydrochloride, chlorinated rubber, hydro-rubber and cyclised rubbers such as may be formed by treating rubber with p.phenol-sulphonic acid; and synthetic rubbers such as polyvinyl chloride, poly-isobutylene and co-polymers of isobutylene with isoprene. The chief importance of the invention however is in connection with the production of rubber-coated articles, particularly tires, in which the coating comprises natural rubber and/or a butadiene rubber, e. g. a polymer of butadiene with styrene, isobutylene or acrylonitrile or of monochlorbutadiene.

The following examples are given to illustrate the invention.

Example 1 Precipitated calcium carbonate was milled for 96 hours with a 7.5% solution of cellulose acetate in acetone to form a slurry containing 25% by weight of carbonate. Sufficient of the slurry was mixed with a spinning solution consisting of 26% of cellulose acetate in acetone to give 2% of carbonate on the weight of the cellulose acetate and the solution was then dry spun to give a yarn of 150 denier, the filament denier being 15. The yarn was stretched to ten times its original length during its travel through wet steam at a temperature of 135 C. and was taken up on another bobbin. It was then hanked and completely saponified in hank form in an aqueous solution at a temperature of C. containing Az% sodium hydroxide and 10% sodium acetate. When saponification was complete the hanks were removed from the saponifying liquid and immersed in a solution of hydrochloric acid at 20 to 25 C. until removal of calcium carbonate from the surface layers of the filaments had been effected. The yarn was then thoroughly washed, first with water, then with a dilute solution of sodium carbonate and then again with water, after which it was dried.

Example 2 A yarn made of acetone-soluble cellulose acetate was immersed in hank form for about 5 to 15 minutes in an aqueous solution containing 30% of acetone and 5% magnesium carbonate. The yarn was then removed, washed and dried, after which it was Wound on bobbins and stretched and saponified as described in Example 1. Finally it was immersed in hank form in a 10% solution of acetic acid until the magnesium carbonate had been removed, after which it was washed with water and dried.

Example 3 Regenerated cellulose yarn obtained as de- 7 scribed in either of the preceding examples was assembled and twisted to form cords from which a tire fabric was woven. The fabric was given a skim coating of rubber containing suitable vulcanising agents during its passage through a calender, the coating was vulcanised and the coated fabric was used in the production of tires.

Havin described my invention, what I desire to secure by Letters Patent is:

1. Process for the production of high tenacity artificial yarns suitable for coating with rubber, which comprises applying to a cellulose acetate yarn while in a swollen condition a finely divided substance Which is insoluble in water but soluble in dilute acids, stretching the treated yarn while it is softened by contact with an aqueous medium at a temperature above 100 C., and washing the stretched yarn with a dilute acid whereby the finely divided material is removed from the yarn.

2. Process for the production of high tenacity artificial yarns suitable for coating with rubber, which comprises applying to a cellulose acetate yarn while in a swollen condition a finely divided water-insoluble metal carbonate, stretching the treated yarn while it is softened by contact with an aqueous medium at a temperature of 130- 145 C. and washing the stretched yarn with a dilute acid whereby the finely divided metal carbonate is removed from the yarn.

3. Process for the production of high tenacity artificial yarns suitable for coating with rubber, which comprisesapplying to a cellulose acetate yarn while in a swollen condition a finely divided calcium carbonate, stretching the treated yarn while it is softened by contact with an aqueous medium at a temperature of 130-145 0., and washing the stretched yarn with a dilute acid whereby the finely divided calcium carbonate is removed from the yarn.

4. Process for the production of high tenacity artificial yarns suitable for coating with rubber, which comprises applying to a cellulose acetate yarn while in a swollen condition a finely divided water-insoluble metal carbonate, stretching the treated yarn in contact with wet steam at a temperature of 130-145 C., and washing the stretched yarn with a dilute acid whereby the finely divided metal carbonate is removed from the yarn.

5. Process for the production of high tenacity artificial yarns suitable for coating with rubber, which comprises applying to a cellulose acetate yarn while in a swollen condition a finely divided calcium carbonate, stretching the treated yarn in contact with wet steam at a temperature of 130- 145 C., and washing the stretched yarn with a dilute acid whereby the finely divided calcium carbonate is removed from the yarn.

6. Process for the production of high tenacity artificial yarns suitable for coating with rubber, which comprises applying to a cellulose acetate yarn while in a swollen condition a finely divided water-insoluble metal carbonate, stretching the treated yarn while it is softened by contact with an aqueous medium at a temperature of 130- 145 C., substantially completely saponifying the stretched yarn by means of an alkaline saponifying medium, and washing the regenerated cellulose yarn so produced with a dilute acid whereby the finely divided metal carbonate is removed from the yarn.

7. Process for the production of high tenacity artificial yarns suitable for coating with rubber, which comprises applying to a cellulose acetate yarn while in a swollen condition a finely divided calcium carbonate, stretching the treated yarn while it is softened by contact with an aqueous medium at a temperature of 130145 C., substantially completely saponifying the stretched yarn by means of an alkaline saponifying medium, and washing the regenerated cellulose yarn so produced with a dilute acid whereby the finely divided calcium carbonate is removed from the yarn.

8. Process for the production of composite articles comprising rubber-coated high tenacity yarns, which comprises applying to a cellulose acetate yarn while in a swollen condition a finely divided substance which is insoluble in water but soluble in dilute acids, stretching the treated yarn while it is softened by contact with an aqueous medium at a temperature above C., washing the stretched yarn with a dilute acid whereby the finely divided material is removed from the yarn, and then coating the yarn with rubber.

9. Process for the production of composite articles comprising rubber-coated high tenacity yarns, which comprises applying to a cellulose acetate yarn while in a swollen condition finely divided calcium carbonate, stretching the treated yarn in contact with wet steam at a temperature of l30-145 C., substantially completely saponifying the stretched yarn by means of an alkaline saponifying medium, washing the regenerated cellulose yarn so produced with a dilute acid whereby the finely divided calcium carbonate is removed from the yarn, and coating the yarn with rubber.

10. Process according to claim 9, wherein the yarn is coated with natural rubber.

11. Process according to claim 9, wherein the yarn is coated with a butadiene rubber.

THOMAS JACKSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Num er Name Date Re.18,170 Lilienfeld Aug. 25, 1931 1,629,241 Ubbelohde May 1'7, 1927 1,770,310 Karplus July 8, 1930 1,935,203 Dreyfus et a1 Nov. 14, 1933 1,983,349 Dreyfus Dec. 4, 1934 2,040,105 Ritzert May 12, 1936 2,052,590 Whitehead Sept. 1, 1936 2,053,123 Alles Sept. 1, 1936 2,053,310 Altwegg et a1 Sept. 8, 1936 2,090,560 Ubbelohde Aug. 17, 1937 2,112,275 Dreyfus Mar. 29, 1938 2,145,076 Ehrenstein Jan. 24, 1939 2,155,410 Dreyfus Apr. 25, 1939 2,166,740 Karplus July 18, 1939 2,166,741 Karplus July 18, 1939 2,200,946 Bloch May 14, 1940 2,331,610 Kemp Oct. 12, 1943 

1. PROCESS FOR THE PRODUCTION OF HIGH TENACITY ARTIFICAL YARNS SUITABLE FOR COATING WITH RUBBER, WHICH COMPRISES APPLYING TO A CELLULOSE ACETATE YARN WHILE IN A SWOLLEN CONDITION A FINELY DIVIDED SUBSTANCE WHICH IS INSOLUBLE IN WATER BUT SOLUBLE IN DILUTE ACIDS, STRETCHING THE TREATED YARN WHILE IT IS SOFTENED BY CONTACT WITH AN AQUEOUS MEDIUM AT A TEMPERATURE ABOVE 100*C., AND WASHING THE STRETCHED YARN WITH A DILUTE ACID WHEREBY THE FINELY DIVIDED MATERIAL IS REMOVED FROM THE YARN. 